[openstack-dev] [nova] [neutron] Should we continue providing FQDNs for instance hostnames?

Stephen Finucane sfinucan at redhat.com
Mon Sep 4 12:48:45 UTC 2017

On Mon, 2017-09-04 at 11:51 +0000, Gary Kotton wrote:
> On 9/4/17, 11:18 AM,
"Stephen Finucane" <sfinucan at redhat.com> wrote:
> > Nova has a feature whereby
it will provide instance host names that cloud-
> > init can extract and use
inside the guest, i.e. this won't happen without
> > cloud-init. These host
names are fully qualified domain names (FQDNs) based
> > upon the instance name
and local domain name. However, as noted in bug
> > #1698010 [1], the domain
name part of this is based up nova's 'dhcp_domain'
> > option, which is a nova-
network option that has been deprecated [2].
> >     
> > I've started work on a
fix [3] that will allow us to retrieve this
> > information from neutron
instead, uncoupling us from this legacy option.
> > However, some commentators
have pointed out that this may not necessarily 
> > be what we want to do: a
FQDN is a hostname and domain name, and using one 
> > as a hostname may not be
that clever nor correct.
> >
> > My networking fu isn't strong enough to deliver
a verdict so I'm hoping
> > someone else can make my mind up for me: do we want
to migrate this feature
> > to neutron, or do we want to stop using FQDN and
just use instance names?
> Hi,
> Your patch https://review.openstack.org/#/c/48
0616/ requires that neutron
> expose the ‘DNS Integration’ extension be support
by neutron and the relevant
> networking plugin. If it does not then will be a
regression and things will
> not work.
> In addition to this that is per network
and not global so there will also be
> a regression for running instances if
nova is updated.

OK, so ultimately this isn't something we can rely on from neutron? Does that
mean we should abandon the idea of providing FQDN when using neutron? Mores to
the original point, is there any reason we would want to/should use FQDN?


> > [1] https://bugs.launchpad.net/nova/+bug/1698010
> > [2] https://review.openstack.org/#/c/395683/
> > [3] https://review.openstack.org/#/c/480616/

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